Liquefied gas producing facility and liquefied gas producing method

ABSTRACT

A liquefied gas producing facility is provided and includes: a first heat exchanger, a first refrigerant compressor, a second heat exchanger, a second refrigerant compressor, air-cooling heat exchangers for a first refrigerant, air-cooling condensers for a first refrigerant, air-cooling heat exchangers for a second refrigerant, air-cooling condensers for a second refrigerant and a mist spraying device. The liquefied gas producing facility can produce liquefied gas by liquefying feed gas which contains methane as a main component.

TECHNICAL FIELD

The present invention relates to a liquefied gas producing facility and a liquefied gas producing method.

BACKGROUND ART

Liquefied gas producing facilities are facilities for producing desired liquefied gas by refining and liquefying liquefied natural gas (LNG), liquefied petroleum gas (LPG), and synthetic natural gas (SNG), which are natural gases. Examples of liquefied gas producing facilities include an LNG producing facility, an LPG producing facility, and an SNG producing facility.

Refrigeration cycles of LNG producing facilities include water-cooling or air-cooling condensers. Water-cooling condensers often use seawater to cool cooling water. However, the influence of the seawater heated as a result of heat exchange on the environment has become a problem, and the number of LNG producing facilities including air-cooling condensers has recently increased.

A liquefaction process is essential not only in LNG producing facilities but also in LPG producing facilities and SNG producing facilities.

As illustrated in FIGS. 1 and 2 of PTL 1, a typical LNG producing facility is configured such that a pipe rack is arranged in a central area of the facility and compressors, heat exchangers for cooling natural gas, a distillation column for refining the natural gas, etc., are arranged on both sides of the pipe rack. In an LNG producing facility including an air-cooling condenser, a plurality of air fin coolers (hereinafter referred to also as “AFCs”) are installed at the top of the pipe rack. The AFCs suck in air from below with fans, cause the air to exchange heat with fluids that flow through tubes arranged on the pipe rack, and discharge the air heated as a result of the heat exchange upward.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2005-147568

SUMMARY OF INVENTION Technical Problem

In LNG producing facilities including air-cooling heat exchangers, as the outside temperature increases, the amount of heat exchange in the AFCs decreases, and the output of gas turbines decreases accordingly. This leads to a reduction in the amount of production of LNG.

Accordingly, an object of the present invention is to provide an air-cooling liquefied gas producing facility and an air-cooling liquefied gas producing method with which the efficiency of heat exchange performed by the AFCs can be increased and a reduction in the amount of production of liquefied gas due to outside temperature can be suppressed.

Solution to Problem

According to the present invention, a liquefied gas producing facility and the like as described in the following items can be provided.

1. A liquefied gas producing facility which produces liquefied gas by liquefying feed gas which contains methane as a main component, the liquefied gas producing facility comprising:

a first heat exchanger that causes a first refrigerant to exchange heat with the feed gas and a second refrigerant to cool the feed gas and the second refrigerant;

a first refrigerant compressor that compresses the first refrigerant that is gasified through cooling the feed gas and the second refrigerant in the first heat exchanger;

a second heat exchanger that causes the second refrigerant to exchange heat with the feed gas that is cooled by the first heat exchanger to further cool and liquefy the feed gas;

a second refrigerant compressor that compresses the second refrigerant that is gasified through cooling the feed gas in the second heat exchanger;

air-cooling heat exchangers for the first refrigerant that air-cool the first refrigerant that is discharged from the first refrigerant compressor;

air-cooling condensers for the first refrigerant that air-cool the first refrigerant that is cooled by the air-cooling heat exchangers for the first refrigerant to liquefy the first refrigerant;

air-cooling heat exchangers for the second refrigerant that air-cool the second refrigerant that is discharged from the second refrigerant compressor;

air-cooling condensers for the second refrigerant that air-cool the second refrigerant that is cooled by the air-cooling heat exchangers for the second refrigerant to liquefy the second refrigerant; and

a mist spraying device that sprays a mist containing demineralized water toward cooling air supplied to at least one of the air-cooling condensers for the first refrigerant.

If the demineralized water is sprayed to all air-cooling heat exchangers (hereunder, “heat exchanger” may also include “condenser”) that the liquefied gas producing facility comprises, an amount of heat exchanged in the heat exchangers increases and an amount of production is maximized. However, it requires a huge amount of demineralized water and is not economical. Therefore, by specifying the air-cooling heat exchangers to which the demineralized water is splayed, the consumption of demineralized water is reduced and an LNG production capacity is efficiently improved.

In the air-cooling condensers for the first refrigerant, the feed gas and the second refrigerant are cooled by indirectly exchanging heat with the first refrigerant. The second refrigerant for liquefying the feed gas is cooled by the first refrigerant, and thus, if the refrigeration capacity of the first refrigerant is decreased, the production capacity of the liquefied gas producing facility is significantly decreased.

Therefore, in item 1 above, the mist is sprayed to one of the air-cooling condensers for the first refrigerant, thereby reducing the consumption of demineralized water and efficiently improving an LNG production capacity.

2. The liquefied gas producing facility according to item 1, further comprising:

an acid gas removing device that removes acid gas contained in the feed gas with an amine solution; and

a demineralized water producing device that produces demineralized water for diluting the amine solution,

wherein the demineralized water contained in the mist is supplied from the demineralized water producing device.

3. The liquefied gas producing facility according to item 1 or 2,

wherein said at least one of the air-cooling condensers for the first refrigerant that are sprayed with the mist includes an air-cooling condenser for the first refrigerant on which an influence of hot air recirculation (HAR) is large and which is determined on the basis of meteorological field information concerning an area around a location at which the liquefied gas producing facility is installed, the meteorological field information being computed by using three-dimensional fluid dynamic equations.

Further, by HAR wherein hot air discharged from one AFC is drawn in the other AFC, there is a problem that the amount of heat exchanged in AFCs is reduced and the production of liquefied gas is decreased. In item 3 above, this problem is avoided.

4. The liquefied gas producing facility according to item 3,

wherein the meteorological field information concerning an area around a location at which the liquefied gas producing facility is installed is calculated by the steps of:

selecting, from a plurality of weather information which are related to areas and times and which include at least temperature data, a plurality of weather information sets related to a plurality of times over a fixed period concerning a first area containing a location at which the liquefied gas producing facility is installed;

solving, with the use of the selected plurality of weather information sets as input data, differential equations expressing the weather information based on an analysis model used for conducting a weather simulation, and generating a plurality of first narrow-area weather information sets related to a plurality of second areas which are disposed within the first area and which are smaller than the first area; selecting a second narrow-area weather information set concerning a second area containing the location at which the liquefied gas producing facility is installed from among the generated plurality of first narrow-area weather information sets; and computing the second narrow-area weather information set by using three-dimensional fluid dynamic equations and calculating the meteorological field information concerning the area around the location at which the liquefied gas producing facility is installed.

5. A method for producing liquefied gas by liquefying feed gas which contains methane as a main component, the method comprising the steps of:

causing, by using a first heat exchanger, a first refrigerant to exchange heat with the feed gas and a second refrigerant to cool the feed gas and the second refrigerant;

compressing, by using a first refrigerant compressor, the first refrigerant that is gasified through cooling the feed gas and the second refrigerant in the first heat exchanger;

causing, by using a second heat exchanger, the second refrigerant to exchange heat with the feed gas that is cooled by the first heat exchanger to further cool and liquefy the feed gas;

compressing, by using a second refrigerant compressor, the second refrigerant that is gasified through cooling the feed gas in the second heat exchanger;

air-cooling, by using air-cooling heat exchangers for the first refrigerant, the first refrigerant that is discharged from the first refrigerant compressor;

air-cooling, by using air-cooling condensers for the first refrigerant, the first refrigerant that is cooled by the air-cooling heat exchangers for the first refrigerant to liquefy the first refrigerant;

air-cooling, by using air-cooling heat exchangers for the second refrigerant, the second refrigerant that is discharged from the second refrigerant compressor; air-cooling, by using air-cooling condensers for the second refrigerant, the second refrigerant that is cooled by the air-cooling heat exchangers for the second refrigerant to liquefy the second refrigerant; and

spraying a mist containing demineralized water toward cooling air supplied to at least one of the air-cooling condensers for the first refrigerant.

6. The method for producing liquefied gas according to item 5, further comprising the steps of:

removing, by using an acid gas removing device, acid gas contained in the feed gas with an amine solution; and

producing, by using a demineralized water producing device, demineralized water for diluting the amine solution,

wherein the demineralized water contained in the mist is supplied from the demineralized water producing device.

7. The method for producing liquefied gas according to item 5 or 6,

wherein said at least one of the air-cooling condensers for the first refrigerant that are sprayed with the mist includes an air-cooling condenser for the first refrigerant on which an influence of hot air recirculation (HAR) is large and which is determined on the basis of meteorological field information concerning an area around a location at which the liquefied gas producing apparatus is installed, the meteorological field information being computed by using three-dimensional fluid dynamic equations.

8. The method for producing liquefied gas according to item 7,

wherein the meteorological field information concerning an area around a location at which the liquefied gas producing facility is installed is calculated by the steps of:

selecting, from a plurality of items of weather information which are related to areas and times and which include at least temperature data, a plurality of weather information sets related to a plurality of times over a fixed period concerning a first area containing a location at which the liquefied gas producing facility is installed;

solving, with the use of the selected plurality of weather information sets as input data, differential equations expressing the weather information based on an analysis model used for conducting a weather simulation, and generating a plurality of first narrow-area weather information sets related to a plurality of second areas which are disposed within the first area and which are smaller than the first area;

selecting a second narrow area weather information set concerning a second area containing the location at which the liquefied gas producing facility is installed from among the generated plurality of first narrow-area weather information sets; and

computing the second narrow area weather information set by using three-dimensional fluid dynamic equations and calculating the meteorological field information concerning the area around the location at which the liquefied gas producing facility is installed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating an example of an LNG producing facility.

FIG. 2 is a schematic diagram illustrating an example of an LNG liquefaction facility.

FIG. 3 illustrates an example of the functional configuration of a weather predicting apparatus.

FIG. 4 illustrates an example of the data table of weather information.

FIG. 5 illustrates an example of the hardware configuration of a weather predicting apparatus.

FIG. 6 illustrates an example of wide-area weather information.

FIG. 7 illustrates an example in which a part of the wide-area weather information illustrated in FIG. 6 is enlarged.

FIG. 8 illustrates an example of narrow-area weather information.

FIG. 9 illustrates an example of meteorological field information.

FIG. 10 illustrates examples of AFCs at which HAR is occurring.

FIG. 11 is a schematic diagram illustrating an embodiment of an LNG liquefaction facility.

FIG. 12 is a schematic diagram illustrating an embodiment of the arrangement of components in an LNG producing facility.

FIG. 13 is a schematic diagram illustrating an embodiment of a demineralized water supply device.

FIG. 14 is a schematic diagram illustrating another embodiment of an LNG liquefaction facility.

DESCRIPTION OF EMBODIMENTS

1. Liquefied gas producing facility

A liquefied gas producing facility according to the present invention air-cools a refrigerant with air-cooling heat exchangers to liquefy gas. All of heat exchangers described below are air-cooling heat exchangers unless otherwise specified in this specification.

FIG. 1 is a schematic diagram illustrating an example of an LNG producing facility. Gas supplied from a gas well is fed to the LNG producing facility after being subjected to a liquid separation process. In the LNG producing facility, LNG is produced by the steps of, for example, mercury removal, acid gas removal, moisture removal, liquefaction, nitrogen removal and the like.

In the liquefaction step, the natural gas is liquefied by a vapor compression refrigeration cycle in which power of a compressor and heat exchange in a condenser are utilized. In the refrigeration cycle, a gas refrigerant is compressed by the compressor and cooled by the condenser, so that the gas refrigerant is converted into a high-pressure liquid. Then, the pressure and temperature of the refrigerant are reduced by an expansion valve or the like, and the refrigerant is caused to exchange heat with the natural gas. The refrigerant is gasified as a result of the heat exchange, and is supplied to the compressor. Thus, the refrigerant is circulated.

The step of acid gas removal is performed by separating acid gas and process gas by chemical absorption separation using an amine solution.

More specifically, a liquefied gas producing facility according to the present invention includes a liquefied gas producing unit which produces liquefied gas by removing unnecessary substances from feed gas, which contains methane as a main component, and by liquefying the feed gas. The liquefied gas producing unit includes a heat exchanger that cools the feed gas by causing the feed gas to exchange heat with a refrigerant, a compressor that compresses the refrigerant vaporized as a result of heat exchange with the feed gas, an AFC unit that cools the compressed refrigerant, and an expansion unit that further cools the cooled refrigerant by adiabatically expanding the refrigerant. The AFC unit includes a demineralized water supply device which sprays demineralized water.

In the liquefied gas producing facility according to the present invention, the demineralized water supply device sprays demineralized water in the form of mists or liquid droplets toward regions below AFCs. The sprayed demineralized water is sucked upward together with air sucked by the AFCs from the regions below. The demineralized water that has been sucked vaporizes while passing between tubes on a pipe rack before being discharged upward from the AFCs. The heat of vaporization generated at this time efficiently cools the refrigerant that flows through the tubes arranged on the pipe rack, so that reduction in the amount of heat exchange due to the outside temperature and HAR can be suppressed. As a result, reduction in the amount of production of the liquefied gas can be suppressed.

The demineralized water is water from which salts are removed. Examples of demineralized water include deionized water that has passed through an ion exchange resin, RO water that has passed through a reverse osmosis membrane, distilled water and the like. When the demineralized water is used, formation of scale on the tubes and the AFCs due to salts can be prevented, and a cause of reduction in heat-transfer co-efficient can be removed.

FIG. 2 is a schematic diagram illustrating an example of a liquefaction facility included in the LNG producing facility.

Feed gas 100 from which CO₂, H₂S, and water, which are typical impurities, are removed is transferred to the liquefaction facility as a process fluid. Then, the feed gas is cooled by two refrigerants having different temperatures, and is finally liquefied. The refrigerant having a higher temperature (“first refrigerant”) is, for example, propane. The refrigerant having a lower temperature (“second refrigerant”) is, for example, a mixed refrigerant containing nitrogen, methane, ethane, and propane.

In FIG. 2, the feed gas is cooled and liquefied by a heat exchanger 101 which uses the first refrigerant as a refrigerant and by a heat exchanger 102 which uses the second refrigerant as a refrigerant. LNG product is transferred to a storage tank 105 by a pump 104, and is stored until shipment. The LNG is slightly heated in the storage tank, and gas is generated as a result of vaporization of the LNG. This gas is returned to the process, liquefied again by the heat exchanger 102, and transferred to the storage tank 105 by the pump 104.

In a first refrigerant refrigeration cycle, the first refrigerant collected through intake lines 203, 204, and 205 is pressurized by a first refrigerant compressor 200, and is then cooled by an air-cooling heat exchanger for the first refrigerant 201. Then, the first refrigerant is liquefied by an air-cooling condenser for the first refrigerant 211, de-compressed to a predetermined pressure by an expansion valve 202, and is transferred to the heat exchanger 101. The heat exchanger 101 cools the feed gas 100 and the second refrigerant, which is used in a downstream heat exchanger, by causing them to exchange heat with the first refrigerant.

In a second refrigerant refrigeration cycle, the second refrigerant collected through intake lines 303 and 304 is pressurized by a second refrigerant compressor 300, and is then cooled by an air-cooling heat exchanger for the second refrigerant 301. Then, the second refrigerant is cooled and liquefied as a result of heat exchange with the first refrigerant in the heat exchanger 101. Next, the second refrigerant is decompressed to a predetermined pressure by an expansion valve 302, and is transferred to the heat exchanger 102. The heat exchanger 102 cools and liquefies the feed gas 100 discharged from the heat exchanger 101.

According to the present invention, a demineralized water supply device (not shown) sprays demineralized water from below an AFC 100A.

2. Liquefied gas producing method

A liquefied gas producing method according to the present invention is a method for producing liquefied gas by removing unnecessary substances from feed gas, which contains methane as a main component, and by liquefying the feed gas. The liquefied gas producing method includes the steps of cooling the feed gas by causing the feed gas to exchange heat with a refrigerant, compressing the refrigerant vaporized as a result of the heat exchange with the feed gas, cooling the compressed refrigerant with AFCs, and further cooling the cooled refrigerant by adiabatically expanding the refrigerant. Demineralized water is sprayed from below the AFCs.

With the liquefied gas producing method according to the present invention, the demineralized water is sprayed from below the AFCs, so that the sprayed demineralized water is sucked upward together with air sucked by the AFCs from below. The demineralized water that has been sucked vaporizes while passing between tubes on a pipe rack before being discharged upward from the AFCs. The heat of vaporization generated at this time efficiently cools the refrigerant that flows through the tubes arranged on the pipe rack, so that reduction in the amount of heat exchange due to the outside temperature and HAR can be suppressed. As a result, reduction in the amount of production of the liquefied gas can be suppressed.

The sprayed demineralized water may be in the form of mists or liquid droplets. Although the diameter of the liquid droplets is not particularly limited, the diameter is preferably as small as possible. The amount of demineralized water to be sprayed may be changed as appropriate in accordance with the outside temperature and the occurrence of HAR. Preferably, the amount of demineralized water to be sprayed is set so that all of the demineralized water is vaporized before being discharged upward from the AFCs.

The AFCs toward which the demineralized water is sprayed are preferably only some of the AFCs used to produce the liquefied gas. To spray the demineralized water toward all the AFCs used to produce the liquefied gas, a large demineralized water supply device is required. In contrast, when the demineralized water is sprayed toward only some of the AFCs, the required amount of demineralized water can be reduced. Accordingly, the equipment cost for producing and spraying the demineralized water and the operation cost can be reduced.

The AFCs toward which the demineralized water is sprayed are preferably the AFCs that have a large influence on the amount of production of the liquefied gas. When the demineralized water is sprayed toward the AFCs that have a large influence on the amount of production of the liquefied gas, the required amount of demineralized water can be reduced. In addition, reduction in the amount of heat exchange and reduction in the amount of production of the liquefied gas due to the outside temperature and HAR can be suppressed.

3. Determination of AFCs toward Which Demineralized Water is to be Sprayed Based on Simulation

The AFCs which have a large influence on the amount of production of the liquefied gas are, for example, AFCs having a large heat transfer area (amount of heat exchange) and AFCs that are greatly influenced by HAR. The influence of HAR can be analyzed by simulation.

3.1 Weather Analysis Models

The descriptions are made on examples of the simulation (computational fluid analysis) that is performed with a weather predicting apparatus using output data of weather analysis models that are to be described below.

When measuring the temperature and the direction of the wind in an area in which a liquefied gas producing facility will be placed, measurements over several years are required since it is necessary to design a liquefied gas producing facility by considering the influence of an annual change, such as whether or not the El Nino phenomenon is observed. However, if there is no data over the years, a liquefied gas producing facility has to be designed on the basis of low-precision environmental data, since it is difficult to measure the temperature and the direction of the wind for several years in future from a present time point.

Weather analysis models include various physical models, and by analyzing such physical models by using a computer, calculations for predicting the weather having a higher spatial resolution are performed, thereby making it possible to conduct weather simulations. Weather simulations have an advantage over field observation that weather information having a higher spatial resolution can be estimated.

In order to conduct weather simulations, it is necessary to load data of initial values and boundary values from a weather database downloaded from a network. A sufficiently detailed spatial resolution for designing an LNG producing facility is not available. However, as weather information concerning a wide area including an area in which an LNG producing facility is placed (hereinafter referred to as a “wide-area weather information”), for example, NCEP (National Centers for Environmental Prediction), which is global observation analysis data reanalyzed every six hours and which is provided by NOAA (National Oceanic and Atmospheric Administration) etc., is available. NCEP data as the wide-area weather information include weather elements (wind direction, wind speed, turbulence energy, solar radiation, atmospheric pressure, precipitation, humidity, and temperature) on three-dimensional grid points obtained by dividing the world into a grid pattern (grid spacing is 1.5 through 400 km), and are updated every six hours. In this embodiment, it is necessary to design an LNG producing facility by considering the influence of an annual change, such as whether or not the El Nino phenomenon is observed. Accordingly, wide-area weather information over the several years (for example, the above-described NCEP data) is used as data of initial values and boundary values.

An example of physical models included in weather analysis models is the WRF (Weather Research & Forecasting Model). The WRF include various physical models. Examples of the physical models are radiation models for calculating the amount of solar radiation and the amount of atmospheric radiation, turbulence models for expressing a turbulence mixed layer, and ground surface models for calculating the ground surface temperature, soil temperature, field moisture, snowfall amount, and surface flux.

The weather analysis models include partial differential equations expressing the motion of fluid in the atmosphere, such as Navier-Stokes equations concerning the motion of fluid and empirical equations derived from atmospheric observation results, and partial differential equations expressing the law of conservation of mass and the law of conservation of energy. By solving these simultaneous partial differential equations, weather simulations can be conducted. Thus, by using wide-area weather information as input data indicating initial values and boundary values, differential equations based on weather analysis models for weather simulations are solved, thereby making it possible to generate weather information concerning a location area of an LNG producing facility related to a region having a narrower spatial resolution than that of wide-area weather information. Weather information generated in this manner is referred to as “narrow-area weather information”.

3.2 Computational Fluid Analysis

Computational fluid analysis refers to a numerical analysis and simulation technique for observing the flow of fluid by applying Computational Fluid Dynamics (CFD) in which equations concerning the motion of fluid are solved by using a computer. More specifically, by using Navier-Stokes equations, which are fluid dynamics equations, the state of fluid is spatially calculated by utilizing the Finite Volume Method. The procedure for computational fluid analysis includes a step of creating 3D model data reflecting a structure of a facility, which is a subject to be examined, a step of generating grids by dividing a range of the subject to be examined into grids, which are the minimum calculation units, a step of loading initial values and boundary values and solving fluid dynamic equations concerning each grid by using a computer, and a step of outputting various values (flow velocity, pressure, etc.) obtained from analysis results, as images, such as contours and vectors.

By conducting computational fluid analysis, fluid simulations having a higher resolution than those obtained by weather analysis models can be implemented. Thus, it is possible to provide information concerning air current phenomena unique to a space scale of a subject to be examined, such as small changes in the wind speed and the wind direction, a disturbance of an air current on a scale from several centimeters to several meters, and a change in air current around a building, which are very difficult to predict by weather simulations.

3.3 Functional Configuration and Hardware Configuration of Weather Predicting Apparatus

A weather predicting apparatus uses weather analysis models or conducts computational fluid analysis, thereby calculating narrow-area weather information concerning a narrow area in which an LNG producing facility is placed.

FIG. 3 illustrates an example of the functional configuration of a weather predicting apparatus. A weather predicting apparatus 90 shown in FIG. 3 includes a storage section 12 which stores therein data and programs and a processor 14 which executes arithmetic operations. In the storage section 12, a weather analysis program 901, such as the WRF, a computational fluid analysis program 903, a design temperature calculating program 905, a wind rose generating program 907, a layout output program 909 for generating a layout, a weather database 800, wide-area weather information 801, such as NCEP data, narrow-area weather information 803 obtained by weather simulations, air flow field information 805 obtained by computational fluid analysis, temperature analysis data 807, wind direction analysis data 808, and layout data 809. The weather database stores therein the wide-area weather information 801, which is obtained as a result of downloading it from an external source or is obtained from a storage medium.

The processor 14 executes the weather analysis program 901 and thereby performs weather analysis processing in which the narrow-area weather information 803 is generated from the wide-area weather information 801 and is stored in the storage section 12. The processor 14 also executes the computational fluid analysis program 903 and thereby performs computational fluid processing in which the air flow field data 807 is generated from the narrow-area weather information 803 and is stored in the storage section 12.

Further, the processor 14 executes the layout generating program 909 and outputs the layout data 809 on the basis of the wind direction analysis data 808.

FIG. 4 illustrates an example of the data table of weather information. The data table shown in FIG. 4 indicates the wide-area weather information 801, but may also be applied to the narrow-area weather information 803. The wide-area weather information indicates weather information concerning a wider area than narrow areas corresponding to the narrow-area weather information, and such a wider area includes the narrow areas corresponding to the narrow-area weather information. The weather information is, as shown in FIG. 4, a plurality of record sets constituted by various data indicating the wind direction, wind speed, turbulence energy, solar radiation, atmospheric pressure, precipitation, humidity, and temperature, by using the time as a primary key. In other words, the data table shown in FIG. 4 is constituted by weather information sets classified based on the temperature, and each of the wide-area weather information 801 and the narrow-area weather information 803 is constituted by a plurality of weather information sets classified based on the area.

FIG. 5 illustrates an example of the hardware configuration of a weather predicting apparatus. The weather predicting apparatus 90 shown in FIG. 5 includes a processor 12A, a main storage device 14A, an auxiliary storage device 14B, which is a hard disk or an SSD (Solid State Drive), a drive 15 that reads data from a storage medium 900, and a communication device 19, such as an NIC (network interface card). These components are connected to one another via a bus 20. The weather prediction apparatus 90 is connected to a display 16, which serves as an output device, and an input device 17, such as a keyboard and a mouse, which are externally disposed. The processor 12 shown in FIG. 3 corresponds to the processor 12A, and the storage section 14 corresponds to the main storage device 14A.

In the storage medium 900, the weather database 800, the weather analysis program 901, the computational fluid analysis program 903, the design temperature calculating program 905, the wind rose generating program 907, and the layout generating program 909 shown in FIG. 3 may be stored as data. These data 800 through 909 are stored in the storage section 12, as shown in FIG. 3.

The weather predicting apparatus 90 may be connected to an external server 200 or a computer 210 or 220 via a network 40. The computer 210 and the external server 200 may have the same components as those of the weather predicting apparatus 90. For example, the weather predicting apparatus 90 may receive the weather database 800 stored in the server 200 via the network 40. Alternatively, among the programs shown in FIG. 3, only the weather analysis program 901 concerning weather simulations having a high system load may be stored in the weather predicting apparatus 90, and the other programs may be stored in any of the computers 210 and 220 and may be executed therein.

Additionally, a description has been given above in which the weather predicting apparatus 90 is restricted to hardware, such as a computer. However, the weather predicting apparatus 90 may be a virtual server in a data center. In this case, the hardware configuration may be as follows. The programs 901 through 909 may be stored in a storage section in a data center, and a processor in the data center may execute the stored programs 901 through 909, and data may be output from the data center to a client computer. The external server 200 may include a weather database, in which case, the weather predicting apparatus 90 may obtain wide-area weather data from the external server 200.

3.4 Reproduction of Weather Information around LNG Producing Facility

FIG. 6 illustrates an example of wide-area weather information. In FIG. 6, wide-area weather information A100 on a map of Japan is shown.

FIG. 7 illustrates an example in which the wide-area weather information shown in FIG. 6 is enlarged. In the wide-area weather information A100 shown in FIG. 7, an area in which the LNG producing facility 100 is placed is shown. Reference numeral 1100 designates a coastline. The left side of the coastline 1100 in the plane of the drawing is the sea, and the right side thereof is the land. FIG. 8 illustrates an example of narrow-area weather information. FIG. 8 illustrates an area for which weather simulations are conducted, and the area is partitioned into a plurality of zones A1 through A16 in order to conduct weather simulations, and each zone corresponds to a calculation grid. For example, if the grid resolution is 9 km, the calculation zone is 549 km×549 km. If the grid resolution is 1 km, the calculation zone is 93 km×93 km. Accordingly, in these zones A1 through A16, estimation points are set in a grid pattern at intervals of 1 through 9 km in the north-south direction and the east-west direction.

The LNG producing facility 100 is placed, as shown in FIG. 8, and in order to obtain the temperature or the direction of the wind in the zone in which the LNG producing facility 100 is placed, the processor 12 generates narrow-area weather information A1 through A16 from the wide-area weather information A100 by solving partial differential equations expressing weather information based on weather analysis models.

FIG. 9 illustrates an example of meteorological field information. The processor 12 conducts computational fluid analysis on the narrow-area weather information A16 shown in FIG. 9, thereby calculating meteorological field information concerning a region smaller than the zones of narrow-area weather information. After calculating the meteorological field information concerning the zone A16, by using the meteorological field information concerning the zone A16 as an initial value, the processor 12 may determine detailed meteorological field information around the LNG producing facility 100 by using fluid dynamic models (CFD models). In this case, the detailed meteorological field information can be determined with a resolution in increments of 0.5 m, which is much smaller than the grid resolution (for example, 1 km) used in weather simulations.

The meteorological field information concerning the target zone A16 in which the LNG producing facility 100 is placed can be determined by using fluid dynamic models. Thus, precise data taking the configurations of buildings into consideration can be obtained. Examples of fluid dynamic models are K-Epsilon, LES, and DNS.

It is sufficient that a computer of this embodiment obtains detailed data of meteorological field information concerning the target zone only, and thus, it is not necessary to conduct analysis for all the zones A1 through A16 by using CFD models. Accordingly, a lot of computation times taken by conducting analysis using CFD models are not necessary, and CFD analysis is conducted only for the target zone, thereby making it possible to improve the precision and decrease the processing time.

Reference numeral 320 shown in FIG. 9 designates a recirculating flow of an exhaust gas. By conducting CFD analysis, the flow in which heated air discharged from the LNG producing facility is returned to and recirculates in the suction unit of the LNG producing facility can be calculated and clarified, which has not been clarified by conducting weather simulations. Additionally, the recirculating flow is clarified, and thus, AFCs that are greatly influenced by HAR can be determined.

Moreover, for example, if there is, for example, an aerodrome in A3 shown in FIG. 8 and required observation data, such as temperature data and wind direction data, is available, first narrow-area weather information sets may be recalculated by using such data as input values. With this arrangement, it is possible to improve the precision of weather simulations by using available local data.

Topographical features of the zone A16 in which the LNG producing facility is placed may be different from those described in weather information due to a reason of any of land leveling, land use, and equipment installation. Even in such a case, first narrow-area weather information sets may be recalculated on the basis of topographical information reflecting any of the land leveling, land use, and equipment installation caused by placing the LNG producing facility. With this arrangement, it is possible to precisely simulate weather conditions after the LNG producing facility is placed.

FIG. 10 illustrates examples of AFCs at which HAR is occurring. FIG. 10 shows that the high/low temperature is indicated by the color shading, and the more the color become dark, the greater the influence of HAR is. The AFCs of propane condenser that greatly influenced by HAR can be determined.

As described above, for the design of the gas liquefaction facility, the narrow-area weather information is provided to predict the weather by the weather simulation, by which the CFD analysis is performed, and thereby the AFCs that HAR is greatly influenced can be clarified. Accordingly, even if there is no available data over the years, it becomes possible to design and construct the gas liquefaction plant in which measures to HAR are considered and implemented.

In the above example, CFD analysis is performed based on calculation results of weather simulation, for the design of gas liquefaction plant; however, CFD analysis can be performed without performing the weather simulation. In that case, CFD analysis can be performed by using the measured weather data, or in case not requiring the higher accuracy.

An air-cooling LNG producing facility includes a plurality of AFCs, and consumption of the demineralized water is increased when the demineralized water is sprayed toward all the AFCs. Therefore, among the air-cooling condenser for the first refrigerant 211, AFCs that are greatly influenced by HAR are determined by simulation, and the demineralized water is sprayed toward the determined AFCs. Thus, the amount of consumption of the demineralized water can be suppressed.

In addition, preferably, CFD analysis is performed and the demineralized water is intermittently sprayed so that the demineralized water is sprayed when the influence of HAR is large. Accordingly, reduction in the amount of production of the liquefied gas due to HAR can be suppressed.

Embodiments of the present invention will now be described below with reference to the accompanying drawings. The scope of the present invention is not limited to the embodiments described below.

Embodiments First Embodiment

FIG. 11 is a schematic diagram illustrating an embodiment of a liquefaction facility included in an LNG producing facility. In this process, propane (hereinafter also referred to as “C3”) and a mixed refrigerant (hereinafter also referred to as “MR”) containing nitrogen, methane, ethane, and propane are used as refrigerants for cooling and liquefying natural gas. This process is referred to as a C3-MR method.

FIG. 11 shows a flow of natural gas (or LNG) which is a process fluid (shown by thin solid lines), a flow of a first refrigeration cycle in which propane is used as a working fluid (shown by thick solid lines), and a flow of a second refrigeration cycle in which the mixed refrigerant is used as a working fluid (shown by dashed lines). The flow of propane and the flow of mixed refrigerant form closed loops through which the respective fluids are circulated by respective compressor driving devices and that are independent of each other. A propane (C3)compressor 20 and two mixed refrigerant (MR) compressors 40 and 42, which are connected in series, are connected to respective gas turbines and motors (not shown) for driving the compressors.

The C3 compressor 20 pressurizes propane, which is the refrigerant of the first refrigeration cycle, and is driven by a single-shaft gas turbine (not shown). The low-pressure-stage MR compressor 40 and the high-pressure-stage MR compressor 42 pressurize the mixed refrigerant, which is a mixture of nitrogen, methane, ethane, and propane and which is the refrigerant of the second refrigeration cycle, in two stages. The MR compressors 40 and 42 are simultaneously driven by a gas turbine and a motor (not shown).

The propane refrigerant pressurized by the C3 compressor 20 circulates through the first refrigeration cycle shown by the thin solid lines, and the mixed refrigerant pressurized by the MR compressors 40 and 42 circulates through the second refrigeration cycle shown by the dashed lines.

Refined natural gas 10, from which carbonic acid gas and hydrogen sulfide are removed in advance by an acid gas processing device, is cooled to about 21 degrees C. under a pressure of about 5 MPa (50 bar) in a heat exchanger 11 through which high-pressure propane refrigerant (pressure 770 kPa (7.7 bar), temperature 17 degrees C.) flows. Accordingly, most of the moisture contained in the refined natural gas 10 is condensed, and is removed afterwards by a drum 12. The thus-dewatered natural gas is cooled to −10 degrees C. in a heat exchanger 13 through which intermediate-pressure propane refrigerant (pressure 320 kPa (3.2 bar), temperature −13 degrees C.) flows, and is then cooled to −30 degrees C. by a heat exchanger 14 through which low-pressure propane refrigerant (pressure 130 kPa (1.3 bar), temperature −37 degrees C.) flows. Next, the natural gas is supplied to a scrub column 15, where heavy fraction is removed. Then, the natural gas is cooled by a main heat exchanger 16 through which the mixed refrigerant of the second refrigeration cycle flows, and is further cooled to −162 degrees C. and liquefied by being adiabatically expanded by an expansion valve 17. The liquefied natural gas is transferred to an LNG tank 18.

In the first refrigeration cycle, the propane refrigerant collected from the heat exchangers 11, 13, and 14 and chillers 24, 25, and 26 is pressurized to 1.6 MPa (16 bar) by the C3 compressor 20. Then, the propane refrigerant is cooled to 47 degrees C., which is close to the condensation temperature, as a result of heat exchange with cooling water in a C3 compressor desuperheater 21, and is further cooled and completely condensed as a result of heat exchange with cooling water in a C3 condenser 22. The condensed propane refrigerant is further cooled by a C3 subcooler 23, decompressed by expansion valves 27 to 32 to respective predetermined pressures, and transferred to each of the heat exchangers 11, 13, and 14 and the chillers 24 to 26.

In the second refrigeration cycle, the mixed refrigerant that has exchanged heat with the natural gas in the main heat exchanger 16 is compressed in two stages by the MR compressors 40 and 42, and is cooled to 45 degrees C. by cooling water in a low-pressure-stage MR compressor aftercooler 41 and a high-pressure-stage MR compressor aftercooler 43. The pressurized mixed refrigerant is successively subjected to heat exchange in the chillers 24 to 26, through which the propane refrigerant decompressed to the respective pressures flows, and is eventually cooled to −35 degrees C. and partially condensed. Then, a separation drum 44 separates the mixed refrigerant into liquid and gas, both of which are caused to flow into the main heat exchanger 16. The mixed refrigerant that has flowed into the main heat exchanger 16 is cooled by being adiabatically expanded by expansion valves 45 and 47, and is dispersed into the main heat exchanger 16 through nozzles 46 and 48. The dispersed mixed refrigerant cools the natural gas by exchanging heat with the natural gas while exchanging heat with the mixed refrigerant that flows through pipes in the main heat exchanger 16.

FIG. 12 is a schematic diagram illustrating the arrangement of components in the LNG producing facility according to the embodiment. Table 1 shows the relationship between the model numbers of the components illustrated in FIG. 12 and the names of the components.

TABLE 1 Model No. Name 1000 Dryer Regen Gas Cooler 1001 Regenerator Overhead Condenser 1002 Demethanizer Bottom Cooler 1003 C3 Condenser 1004 Debutanizer Bottom Cooler 1005 Debutanizer Overhead Condenser 1006 Demethanizer Condenser 1007 Lean Amine Cooler 1008 LP MR Compressor Aftercooler 1009 C3 Subcooler 1010 C3 Compressor Desuperheater 1011 HP MR Compressor Aftercooler 1012 End Flash Gas Compressor Aftercooler 1013 End Flash Gas Compressor 3rd Intercooler 1014 End Flash Gas Compressor 2nd Intercooler 1015 End Flash Gas Compressor 1st Intercooler 1016 MR Gas Turbine 1017 C3 Gas Turbine

FIG. 12 is a schematic top view illustrating the arrangement of the pipe rack disposed in a central region of the LNG producing facility, gas turbines of the C3 compressor (1017), and gas turbines of the MR compressor (1016). A plurality of AFCs are disposed at the top of the pipe rack. The sizes of the components in FIG. 12 reflect the sizes of the areas occupied by the actual components.

Referring to FIG. 12, among the AFCs included in the LNG producing facility, a C3 compressor desuperheater (1010), a C3 condenser (1003), a C3 subcooler (1009), a low-pressure-stage MR compressor aftercooler (1008), and a high-pressure-stage MR compressor aftercooler (1011) occupy large areas on the pipe rack. These AFCs are used for liquefaction, and the heat transfer areas (amounts of heat exchange) thereof are large. Therefore, the effect of spraying of the demineralized water is also large. In particular, the C3 condenser occupies the largest area, and variation in the amount of heat transfer (amount of heat exchange) of the C3 condenser significantly affects the amount of production of the LNG.

Therefore, in the present embodiment, from the viewpoint of occupation areas of the components, the AFCs toward which the demineralized water is to be sprayed are preferably the C3 compressor desuperheater, the C3 condenser, the C3 subcooler, the low-pressure-stage MR compressor aftercooler, and the high-pressure-stage MR compressor aftercooler, and more preferably, the C3 condenser.

The refined natural gas, which is the process fluid, is cooled from ambient temperatures to around −30 degrees C. by propane, and is further cooled to around −162 degrees C. by the mixed refrigerant in the main heat exchanger. Thus, an LNG product is produced. The mixed refrigerant is also cooled from ambient temperatures to around −30 degrees C. by propane, and is then supercooled in the main heat exchanger.

Since both the process fluid and the mixed refrigerant need to be cooled to around −30 degrees C. by propane as described above, reduction in the amount of heat exchange of the propane greatly affects the amount of production of the LNG. The propane is compressed by the C3 compressor 20 to have an increased pressure, and is completely condensed by the C3 condenser 22. The heat of vaporization generated at this time is used to cool the process fluid and the mixed refrigerant to around −30 degrees C. The condensation temperature of the propane depends on the intake temperature of the C3 condenser 22. Therefore, when the intake temperature is increased by the influence of HAR, the pressure increase achieved by the compressor also increases. As a result, energy loss increases.

Therefore, in the present embodiment, from the viewpoint of the process, the AFCs toward which the demineralized water is to be sprayed are preferably those of the C3 condenser 22, and more preferably, some of the AFCs included in the C3 condenser 22 that are greatly affected by HAR.

FIG. 13 is a schematic diagram illustrating an embodiment of a demineralized water supply device.

A demineralized water supply device 70 includes a plurality of spray nozzles 59, and sprays the demineralized water through the spray nozzles 59 so that the cooling air of an AFC can be cooled when the sprayed demineralized water is vaporized. The demineralized water is supplied from a demineralized water tank 50 to a water supply header 57 through a foreign-matter removing strainer 51, a water supply pump 52, a water supply cutoff valve 53, a water-supply-rate control valve 54, a water flowmeter 55, and a foreign-matter removing filter 56. The water supply header 57 guides the supplied water to a plurality of demineralized water pipes. The demineralized water is supplied from the water supply header 57 to the demineralized water pipes through a water-supply-header outlet-flow-rate control valve 58, and is sprayed from the spray nozzles 59. The sprayed demineralized water is sucked upward together with air sucked by an AFC 61. The demineralized water that has been sucked vaporizes while passing between tubes 60 arranged on the pipe rack before being discharged upward from the AFC 61.

A signal representing the amount of supplied demineralized water measured by the water flowmeter 55 is transmitted to a control device 62. The control device 62 is capable of calculating the amount of water required on the basis of the operational state of the AFC 61, and controlling the water-supply-rate control valve 54.

The demineralized water supply device illustrated in FIG. 13 is applied to particular AFCs, such as the C3 condenser, and the demineralized water is sprayed toward the AFCs from below.

Most LNG producing facilities are constructed in a desert or a barren land where a gas well is present, and the surrounding air is generally hot and dry. In particular, during daytime when the sun is up, the maximum temperature increases to around 35 degrees C. The difference between the dry-bulb temperature (temperature of air) and wet-bulb temperature during daytime is often as large as around 10 degrees C. Since the dew point at which water vapor condenses is lower than the wet-bulb temperature, there is a possibility that the air temperature can be reduced to the wet-bulb temperature by about 10 degrees C. by adiabatic cooling achieved by vaporization of the sprayed demineralized water. Thus, it is clear that adiabatic cooling of air introduced into the AFCs by spraying of the demineralized water according to the present invention is very effective.

Second Embodiment

FIG. 14 is a schematic diagram illustrating another embodiment of a liquefaction facility included in an LNG producing facility. In this process, propane, ethylene, and methane are successively used as refrigerants. This process is referred to as a cascade method.

FIG. 14 shows a flow of natural gas (or LNG), which is a process fluid (shown by thin solid lines), a propane cooling cycle in which propane is used as a working fluid (shown by two-dot chain lines), an ethylene cooling cycle in which ethylene is used as a working fluid (shown by dashed lines), and a methane cooling cycle in which methane is used as a working fluid (shown by thick solid lines). The flows of propane, ethylene, and methane form closed loops through which the respective fluids are circulated by respective compressor driving devices and that are independent of each other. A propane compressor 200, an ethylene compressor 300, and a methane compressor 400 are connected to respective gas turbines and motors (not shown) for driving the compressors.

The main components of the propane cooling cycle are the propane compressor 200, a propane cooler 201, a propane condenser 211, an expansion valve 202, a high-pressure intake line 203, an intermediate-pressure intake line 204, and a low-pressure intake line 205.

The main components of the ethylene cooling cycle are the ethylene compressor 300, an ethylene cooler 301, an expansion valve 302, a high-pressure intake line 303, and a low-pressure intake line 304.

The main components of an indirect heat exchange portion of the methane cooling cycle are the methane compressor 400, a methane cooler 401, a high-pressure intake line 402, an intermediate-pressure intake line 403, and a low-pressure intake line 404.

Refined natural gas 100 from which CO₂, H₂S, and water, which are typical impurities, are removed is transferred to the liquefaction facility as a process fluid, and is cooled and liquefied by three heat exchangers with different temperatures that are arranged successively. The three heat exchangers are a heat exchanger 101 which uses propane as a refrigerant, a heat exchanger 102 which uses ethylene as a refrigerant, and a heat exchanger 103 which uses methane as a refrigerant. LNG product is transferred to a storage tank 105 by a pump 104, and is stored until shipment. The LNG is slightly heated in the storage tank and vaporized. The thus-generated gas is returned to the process, liquefied again by the heat exchanger 103, and transferred to the storage tank 105 by the pump 104.

In the propane cooling cycle, the propane refrigerant collected through the intake lines 203, 204, and 205 is pressurized by the propane compressor 200, and is then cooled by the propane cooler 201, and is liquefied by the propane condenser 211. Then, the propane refrigerant is decompressed to a predetermined pressure by the expansion valve 202, and is transferred to the heat exchanger 101. The heat exchanger 101 cools the refined natural gas 100 as well as the ethylene refrigerant and methane refrigerant, which are used in the downstream heat exchangers, by causing them to exchange heat with the propane refrigerant.

In the ethylene cooling cycle, the ethylene refrigerant collected through the intake lines 303 and 304 is pressurized by the ethylene compressor 300, and is then cooled by the ethylene cooler 301. Then, the ethylene refrigerant is further cooled as a result of heat exchange with the propane refrigerant in the heat exchanger 101. Next, the ethylene refrigerant is decompressed to a predetermined pressure by the expansion valve 302, and is transferred to the heat exchanger 102. The heat exchanger 102 cools the refined natural gas 100 discharged from the heat exchanger 101 and the methane refrigerant, which is used in the downstream heat exchanger, by causing them to exchange heat with the propane refrigerant.

In the methane cooling cycle, the methane refrigerant collected through the intake lines 402, 403, and 404 is pressurized by the methane compressor 400, and is then cooled by the methane cooler 401. Then, the methane refrigerant is cooled as a result of heat exchange with the propane refrigerant in the heat exchanger 101, further cooled as a result of heat exchange with the ethylene refrigerant in the heat exchanger 102, and is transferred to the heat exchanger 103. The heat exchanger 103 cools and liquefies the refined natural gas 100 discharged from the heat exchanger 102 by causing it to exchange heat with the methane refrigerant.

Fuel gas 405 is combustible gas which contains a large amount of nitrogen and which has not been liquefied. The fuel gas is used as fuel for gas turbines that drive the compressors. In the case where large power is required to produce the LNG, the amount of fuel gas is increased and the amount of liquefied gas is reduced. When the amount of heat exchange at the AFCs is increased by spraying the demineralized water, the power of the gas turbines can be reduced and the amount of production of the LNG can be maximized.

In the embodiment illustrated in FIG. 14, an AFC toward which the demineralized water is to be sprayed in accordance with the present invention is preferably the propane condenser 211. The demineralized water is sprayed by using the demineralized water supply device illustrated in FIG. 13.

Industrial Applicability

The liquefied gas producing apparatus and liquefied gas producing method according to the present invention are suitable for production of LNG, LPG, and SNG.

Although only some exemplary embodiments and/or examples of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments and/or examples without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.

The documents described in the specification and the Japanese application specification claiming priority under the Paris Convention are incorporated herein by reference in its entirety. 

1. A liquefied gas producing facility which produces liquefied gas by liquefying feed gas which contains methane as a main component, the liquefied gas producing facility comprising: a first heat exchanger that causes a first refrigerant to exchange heat with the feed gas and a second refrigerant to cool the feed gas and the second refrigerant; a first refrigerant compressor that compresses the first refrigerant that is gasified through cooling the feed gas and the second refrigerant in the first heat exchanger; a second heat exchanger that causes the second refrigerant to exchange heat with the feed gas that is cooled by the first heat exchanger to further cool and liquefy the feed gas; a second refrigerant compressor that compresses the second refrigerant that is gasified through cooling the feed gas in the second heat exchanger; air-cooling heat exchangers for the first refrigerant that air-cool the first refrigerant that is discharged from the first refrigerant compressor; air-cooling condensers for the first refrigerant that air-cool the first refrigerant that is cooled by the air-cooling heat exchangers for the first refrigerant to liquefy the first refrigerant; air-cooling heat exchangers for the second refrigerant that air-cool the second refrigerant that is discharged from the second refrigerant compressor; air-cooling condensers for the second refrigerant that air-cool the second refrigerant that is cooled by the air-cooling heat exchangers for the second refrigerant to liquefy the second refrigerant; and a mist spraying device that sprays a mist containing demineralized water toward cooling air supplied to at least one of the air-cooling condensers for the first refrigerant.
 2. The liquefied gas producing facility according to claim 1, further comprising: an acid gas removing device that removes acid gas contained in the feed gas with an amine solution; and a demineralized water producing device that produces demineralized water for diluting the amine solution, wherein the demineralized water contained in the mist is supplied from the demineralized water producing device.
 3. The liquefied gas producing facility according to claim 1, wherein said at least one of the air-cooling condensers for the first refrigerant that are sprayed with the mist includes an air-cooling condenser for the first refrigerant on which an influence of hot air recirculation (HAR) is large and which is determined on the basis of meteorological field information concerning an area around a location at which the liquefied gas producing facility is installed, the meteorological field information being computed by using three-dimensional fluid dynamic equations.
 4. The liquefied gas producing facility according to claim 3, wherein the meteorological field information concerning an area around a location at which the liquefied gas producing facility is installed is calculated by the steps of: selecting, from a plurality of weather information which are related to areas and times and which include at least temperature data, a plurality of weather information sets related to a plurality of times over a fixed period concerning a first area containing a location at which the liquefied gas producing facility is installed; solving, with the use of the selected plurality of weather information sets as input data, differential equations expressing the weather information based on an analysis model used for conducting a weather simulation, and generating a plurality of first narrow-area weather information sets related to a plurality of second areas which are disposed within the first area and which are smaller than the first area; selecting a second narrow-area weather information set concerning a second area containing the location at which the liquefied gas producing facility is installed from among the generated plurality of first narrow-area weather information sets; and computing the second narrow-area weather information set by using three-dimensional fluid dynamic equations and calculating the meteorological field information concerning the area around the location at which the liquefied gas producing facility is installed.
 5. A method for producing liquefied gas by liquefying feed gas which contains methane as a main component, the method comprising the steps of: causing, by using a first heat exchanger, a first refrigerant to exchange heat with the feed gas and a second refrigerant to cool the feed gas and the second refrigerant; compressing, by using a first refrigerant compressor, the first refrigerant that is gasified through cooling the feed gas and the second refrigerant in the first heat exchanger; causing, by using a second heat exchanger, the second refrigerant to exchange heat with the feed gas that is cooled by the first heat exchanger to further cool and liquefy the feed gas; compressing, by using a second refrigerant compressor, the second refrigerant that is gasified through cooling the feed gas in the second heat exchanger; air-cooling, by using air-cooling heat exchangers for the first refrigerant, the first refrigerant that is discharged from the first refrigerant compressor; air-cooling, by using air-cooling condensers for the first refrigerant, the first refrigerant that is cooled by the air-cooling heat exchangers for the first refrigerant to liquefy the first refrigerant; air-cooling, by using air-cooling heat exchangers for the second refrigerant, the second refrigerant that is discharged from the second refrigerant compressor; air-cooling, by using air-cooling condensers for the second refrigerant, the second refrigerant that is cooled by the air-cooling heat exchangers for the second refrigerant to liquefy the second refrigerant; and spraying a mist containing demineralized water toward cooling air supplied to at least one of the air-cooling condensers for the first refrigerant.
 6. The method for producing liquefied gas according to claim 5, further comprising the steps of: removing, by using an acid gas removing device, acid gas contained in the feed gas with an amine solution; and producing, by using a demineralized water producing device, demineralized water for diluting the amine solution, wherein the demineralized water contained in the mist is supplied from the demineralized water producing device.
 7. The method for producing liquefied gas according to claim 5, wherein said at least one of the air-cooling condensers for the first refrigerant that are sprayed with the mist includes an air-cooling condenser for the first refrigerant on which an influence of hot air recirculation (HAR) is large and which is determined on the basis of meteorological field information concerning an area around a location at which the liquefied gas producing apparatus is installed, the meteorological field information being computed by using three-dimensional fluid dynamic equations.
 8. The method for producing liquefied gas according to claim 7, wherein the meteorological field information concerning an area around a location at which the liquefied gas producing facility is installed is calculated by the steps of: selecting, from a plurality of items of weather information which are related to areas and times and which include at least temperature data, a plurality of weather information sets related to a plurality of times over a fixed period concerning a first area containing a location at which the liquefied gas producing facility is installed; solving, with the use of the selected plurality of weather information sets as input data, differential equations expressing the weather information based on an analysis model used for conducting a weather simulation, and generating a plurality of first narrow-area weather information sets related to a plurality of second areas which are disposed within the first area and which are smaller than the first area; selecting a second narrow-area weather information set concerning a second area containing the location at which the liquefied gas producing facility is installed from among the generated plurality of first narrow-area weather information sets; and computing the second narrow-area weather information set by using three-dimensional fluid dynamic equations and calculating the meteorological field information concerning the area around the location at which the liquefied gas producing facility is installed.
 9. The liquefied gas producing facility according to claim 2, wherein said at least one of the air-cooling condensers for the first refrigerant that are sprayed with the mist includes an air-cooling condenser for the first refrigerant on which an influence of hot air recirculation (HAR) is large and which is determined on the basis of meteorological field information concerning an area around a location at which the liquefied gas producing facility is installed, the meteorological field information being computed by using three-dimensional fluid dynamic equations.
 10. The method for producing liquefied gas according to claim 6, wherein said at least one of the air-cooling condensers for the first refrigerant that are sprayed with the mist includes an air-cooling condenser for the first refrigerant on which an influence of hot air recirculation (HAR) is large and which is determined on the basis of meteorological field information concerning an area around a location at which the liquefied gas producing apparatus is installed, the meteorological field information being computed by using three-dimensional fluid dynamic equations. 